Genetic sequencing of protein from T. rex bone confirms dinosaurs' lin...(es of collagen protein from T. rex. ...)

Asara became involved in analysis of the collagen protein because of his expertise in mass spectrometry techniques capable of sequencing minute amounts of protein from human tumors.

For the current work, Organ, Asara and colleagues compared collagen protein from several dozen species. The goal: placing T. rex on the animal kingdom's family tree using molecular evidence.

"Most of the collagen sequence was obtained from protein and genome databases, but we also needed to sequence some critical organisms, including modern alligator and modern ostrich, by mass spectrometry," says Asara.

"We determined that T. rex, in fact, grouped with birds--ostrich and chicken--better than any other organism that we studied," he says. "We also showed that it groups better with birds than modern reptiles, such as alligators and green anole lizards."

While scientists have long suspected that birds, and not more basal reptiles, are dinosaurs' closest living relatives, for years that hypothesis rested largely on morphological similarities in bird and dinosaur skeletons.

The scientists also report that a similar analysis of 160,000- to 600,000-year-old collagen protein sequences derived from a mastodon bone establishes a close phylogenetic relationship between that extinct species and modern elephants.

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